Expression of ICSBP/IRF-8 is required for the acquisition of IDO competence in murine CD8⁺ DCs. (A) RT-PCR analysis of Icsbp1, Tyrobp, and Indo gene expression in CD8⁺ DCs first treated with negative control (nc) or Icsbp1 siRNA for 24 hours and then incubated with medium alone (C) or IFN-γ for 4 hours. cDNA levels were normalized against the Gapdh gene. Results are from 1 of 3 representative experiments. (B) Kynurenine levels in supernatants of CD8⁺ DCs first subjected to siRNA treatment as in panel A and then incubated overnight with medium alone or IFN-γ. Results (mean ± SD) are from 1 of 3 representative experiments.